Anisometrically shaped metal particles, liquid suspensions and films thereof and light valves comprising same

Abstract

The invention is directed to the use of anisometrically shaped metal particles in liquid light valve suspensions, light valve films and light valves. The anisometric metal particles may have various geometric shapes including, for example, fibrils, and an average length in the range between about 1 micron and 50 nanometers.

What is claimed is:  
     
       1. An electro-optical device comprising a cell formed of opposed cell walls, a light modulating unit comprising a suspension containing anisometrically shaped metal particles suspended in a liquid suspending medium between said cell walls and opposed electrodes operatively associated with said cell walls for applying an electrical field across said suspension, wherein said anisometrically shaped metal particles have an average length in a range between about 1 micron and 50 nanometers and an aspect ratio of at least about 3:1. 
     
     
       2. The device according to  claim 1 , wherein said electro-optical device is a light valve and said suspension is a light valve suspension. 
     
     
       3. The device according to  claim 2 , wherein said anisometrically shaped metal particles have an average length between about 50-200 nanometers. 
     
     
       4. The device according to  claim 3 , wherein said anisometrically shaped metal particles have an average length between about 75-180 nanometers. 
     
     
       5. The device according to  claim 1 , wherein said anisometrically shaped metal particles have an aspect ratio of at least about 10:1. 
     
     
       6. The device according to  claim 5 , wherein said anisometrically shaped metal particles have an aspect ratio of at least about 20:1. 
     
     
       7. The device according to  claim 3 , wherein said anisometrically shaped metal particles are in a form selected from the group consisting of rods, cylinders, plates, needles, blades and prisms. 
     
     
       8. The device according to  claim 3 , wherein said anisometrically shaped metal particles are metal fibrils. 
     
     
       9. The device according to  claim 3 , wherein said anisometrically shaped metal particles are prepared in the form of a nanobelt. 
     
     
       10. The device according to  claim 9 , wherein said anisometrically shaped metal particles are formed from a semi-conducting metal oxide. 
     
     
       11. The device according to  claim 10 , wherein said semi-conducting metal oxide is tin oxide or zinc oxide. 
     
     
       12. The device according to  claim 2 , wherein said anisometrically shaped metal particles are formed from a metal selected from the group consisting of gold, platinum, palladium, cobalt, iron, copper, molybdenum and bismuth. 
     
     
       13. The device according to  claim 2 , wherein said anisometrically shaped metal particles have an average diameter ranging from about 3 nanometers to about 333 nanometers. 
     
     
       14. The device according to  claim 13 , wherein said anisometrically shaped metal particles have an average diameter ranging from about 3 nanometers to about 66 nanometers. 
     
     
       15. The device according to  claim 1 , wherein said light modulating unit is a liquid suspension or a film. 
     
     
       16. In a liquid light valve suspension the improvement comprising a plurality of anisometrically shaped metal particles suspended therein, wherein said anisometrically shaped metal particles have an average length in a range between about 1 micron and 50 nanometers and an aspect ratio of at least about 3:1. 
     
     
       17. The suspension of  claim 16 , wherein said anisometrically shaped metal particles are metal fibrils. 
     
     
       18. The suspension of  claim 16 , wherein said anisometrically shaped metal particles are in a form selected from the group consisting of rods, cylinders, plates, needles, blades and prisms. 
     
     
       19. The suspension according to  claim 16 , wherein said anisometrically shaped metal particles are prepared in the form of a nanobelt. 
     
     
       20. The suspension according to  claim 19 , wherein said anisometrically shaped metal particles are formed from a semi-conducting metal oxide. 
     
     
       21. The suspension according to  claim 16 , wherein said anisometrically shaped metal particles are formed from a metal selected from the group consisting of gold, platinum, palladium, cobalt, iron, copper, molybdenum and bismuth. 
     
     
       22. The suspension according to  claim 16 , wherein said anisometrically shaped metal particles have an average diameter ranging from about 3 nanometers to about 333 nanometers. 
     
     
       23. A film suitable for use as the light modulating unit of an SPD light valve, said film comprising a cross-linked polymer matrix and having droplets of a liquid light valve suspension distributed in the cross-linked polymer matrix, said liquid light valve suspension comprising a plurality of anisometrically shaped metal particles suspended in a liquid suspending medium, wherein said anisometrically shaped metal particles have an average length between about 1 micron and 50 nanometers and an aspect ratio of at least about 3:1. 
     
     
       24. The film according to  claim 23 , wherein said anisometrically shaped metal particles are metal fibrils. 
     
     
       25. The film according to  claim 23 , wherein said anisometrically shaped metal particles are in a form selected from the group consisting of rods, cylinders, plates, needles, blades and prisms. 
     
     
       26. The film according to  claim 23 , wherein said anisometrically shaped metal particles are prepared in the form of a nanobelt. 
     
     
       27. The film according to  claim 26 , wherein said anisometrically shaped metal particles are formed from a semi-conducting metal oxide. 
     
     
       28. The film according to  claim 23 , wherein said anisometrically shaped metal particles are formed from a metal selected from the group consisting of gold, platinum, palladium, cobalt, iron, copper, molybdenum and bismuth. 
     
     
       29. The film according to  claim 23 , wherein said anisometrically shaped metal particles have an average diameter ranging from about 3 nanometers to about 333 nanometers. 
     
     
       30. A method of preparing anisometrically shaped metal particles for use in an electro-optical device, said particles having an average length in a range between about 1 micron and 50 nanometers, said method comprising forming a sheet or a film of a metal particle forming material by depositing said particle forming material on to a substrate and subsequently cutting said sheet or said film into said particles by scoring said sheet or said film with a laser. 
     
     
       31. The method of  claim 30  wherein said substrate is soluble in a chosen solvent and wherein, after scoring with said laser, the particles are removed from the substrate by dissolving said substrate with the solvent. 
     
     
       32. A film suitable for use as the light modulating unit of an SPD light valve, said film comprising a polymer matrix and having droplets of a liquid light valve suspension distributed in the polymer matrix, said liquid light valve suspension comprising a plurality of anisometrically shaped metal particles suspended in a liquid suspending medium, wherein said anisometrically shaped metal particles have an average length between about 1 micron and 50 nanometers and an aspect ratio of at least about 3:1. 
     
     
       33. The film according to  claim 32 , wherein said anisometrically shaped metal particles have an average length between about 50-200 nanometers. 
     
     
       34. The film according to  claim 32 , wherein said anisometrically shaped metal particles have an aspect ratio of at least about 10:1. 
     
     
       35. The film according to  claim 32 , wherein said polymer matrix is cross-linked. 
     
     
       36. The film according to  claim 32 , wherein said anisometrically shaped metal particles are metal fibrils. 
     
     
       37. The film according to  claim 32 , wherein said anisometrically shaped metal particles are in a form selected from the group consisting of rods, cylinders, plates, needles, blades and prisms. 
     
     
       38. The film according to  claim 32 , wherein said anisometrically shaped metal particles are in the form of a nanobelt. 
     
     
       39. The film according to  claim 38 , wherein said anisometrically shaped metal particles are formed from a semi-conducting metal oxide. 
     
     
       40. A method of preparing anisometrically shaped metal particles for use in an electro-optical device, said particles having an average length in a range between about 1 micron and 50 nanometers, said method comprising providing a substrate of a metal-particle-forming material, wherein said substrate is highly anisometric in shape, and comminuting said substrate to form a plurality of said anisometrically shaped metal particles, said particles having an aspect ratio of at least about 3:1. 
     
     
       41. The method of  claim 40  wherein said substrate is a sheet or a film of said metal-particle-forming material. 
     
     
       42. The method of  claim 43  wherein said substrate is a metal nanowire. 
     
     
       43. The method of claim 45 wherein said nanowire is comminuted by slicing said nanowire with a microtome into metal fibrils having appropriate lengths.